1. Field of the Invention
The present invention relates to an apparatus capable of adjusting a torque of a moving portion such as an extender having a zoom lens, a focusing lens or an iris stop built therein.
2. Related Background Art
In a conventional art photographing apparatus of this type, a drive unit having a drive motor built therein is provided to conduct power-driven zooming of focusing, etc. The drive unit usually includes switching means for disconnecting an output transmission path of the drive motor so that manual operation is permitted. In such a case, in order to enhance a touch feeling of the manual operation, viscosity of grease and the like is utilized or a friction member is pressed to a manipulation ring to increase an operation torque.
However, in the conventional art, the magnitude of the operation torque is constant and the torque which is to be small for the power-driven operation is increased for the manual operation resulting in the increase of a power consumption, or the power consumption is suppressed at the sacrifice of the touch feeling in the manual operation.
It is disadvantageous and that very time consuming taken to set an operation torque which is compatible to both the power operation and the manual operation.
Even if the operation torque is set to be compatible with both operations, the operation torque desired by the photographer, objects to be photographed and photographing environments are varied. Therefore, photographers are not all satisfied.